[JohnStone]

Hi folks,
decided to chime in after blowing :-( my "China Bang Board" as well and finding later your very helpful thread. Now waiting for the delivery of parts to replace.
Thanks a lot to all individuals sharing the fruits of your personal effort! :-)
After studying the schematic and reading all posts I understand more of the blowing of my drivers and want to forwad my notions:

1.
The 6560 requires to get the 5V first and later it will accept the motor voltage. The schemtic of this board reverses this requirement! :-( Constantly! Let me explain:
The 12V and 5 V regulator along with their capacitors perform a delayline for the 5V supply. It takes some milliseconds until the 5V is stable on the drivers.
Ignoring this the Motor supply is directed to the drivers instantly.

So accept my good advice: DO NOT do what I did - to set a switch between 24V supply and the board. It will blow soon your drivers because of this weakness mentioned above.
If you switch the mains at the input of your power supply you still do not face the power requirements but usually the drivers seem to accept this - most times. But this is still not a recommended use case!

Cause of damage:
The transistors in the output driver are aranged in an H-bridge. It is essential to GARANTEE at every time that within one pole of the H there is only one single transistor switched on at a time. This can not be done without the 5v being stable on the driver! So it is very probable that the too early voltage for the motor drive will open both transistors by itself and a short circuit will occure.
In my case it occured long enough to damge the whole driver. In other cases (switched mains) it will probably crack some parts of it so the output might still do some performance but not full spec or it will be killed later on.

An extra problem seems to be if a motor output is not conneced. My 4 channel bord was connected to X,Y,Z leaving C open. This open channel was blown first. Later Z while not being connected ..... I remember that one of you experienced the same kind of bang. This can be promoted by the heat sink not being connected to GND.

But PLEASE accept my advice. Do not connect the heat sink anywhere to GND. The currents will disturb on their trace other entities of the schematic. It is not just DC current! The best way would be to connect a lead from one screw of every driver to the corresponding ground Pin 10 or/and 15 but NOT pin 6 (this is the 5V-GND - it should not be disturbed by additional driver currents!)

I believe that this power problem is the main problem of all blown drivers. I shared my notions instantly in order to hopefully save some of your boards - wold wide :-)
Give me some days to evaluate some suggestions to face the power on issue.

2.
Reset schematic:
It is good practice to add a diode in parallel to the pullup resistor (cathode connectod to capacitor side and anode connected to supply). This is necessary in order to discharge the capacitor soon when the supply is switched off. If this is not performed you will get no reset after short interruptions of the supply. Proper reset is essential!

3.
Ther were some quesions around regarding the diods in the power input trace to the board. These are usually used in order to protect the board when reversing power and GND acceidently. Omitting these diodes will blow your board in a very very reliable way - in case of pwer reversal.

4.
Some facts reagerding my setup:
- ISEL mill with cutting area of app. 50cm x 50cm, all ball nuts, 2 Proxxon Motors 300 Watt with power supply (bought defect 200 € - only defect = Z home switch :-)
- all stepper motors 4A
- 4 channel china board (this blue one most of you have) - now blown
- PC tower case with PC living downstairs
- in the upper floor live the PC power supply, the driver board just under the roof with component side down and the 20-30V supply in the CD-drive compartment. The case provides an additional blower for this compartment - i will gladly use this support.

Adavantges of this setup:
While feeding this all in one unit through one single cord the unit has a good genuine GND condition. (I hope to omit optos completely later on) It depends on measurements - to be done.

This setup allowes to supply the on board blower with teh 12 V from the PC power supply.

4.
I feel sad because these china men convert such a good motor driver into a problem zone world wide.
Joke: What about Toshiba sponsoring them in order to increase the world wide demand for parts (spare parts) :-)

If you have additional hints for my setup please feel free to comment. It is good practice to screw an idea through different brains :-)

Regards
John

[Gall]

Just ordered a 5-axis version of this board (probably the new one) plus a digital display.

I haven't modifiet it yet (it works but not very good, now I use it to mill acrylic case for it, later I'll do the fixes).

I found that it IS possible to add optical isolation to this board! Fortunately this version has all optocouplers connected to +5V at one side and to GND at another. Using a permamemt marker I've drawn a line on the board under optocouplers (on both sides where possible) without crossing any PCB traces. Now it's obvious where exactly the sides are connected. It is possible to cut GND and +5V traces to separate input and output sides completely. I'm going to do that and install a dc-dc converter in place of 78xx regulators.

Regarding motor noise and driving problems, I think I'll remove these transistors completely without cutting traces. I was unable to measure capacitances at OSC pin without unsoldering, going to measure frequencies later.

There is one more problem with digital display board. It misses steps! I investigated its design and found that it isusing a MCS-51 compatible microcontroller (STC12C5A08AD) at 24 MHz without any hardware counters. Software polling! It is impossible to use software polling at higher step rates with short pulses. Looking for a way to replace the MCU with a CPLD or something; it were nice to find a pin compatible part but probably it's impossible.

Another problem is that the display is very dim. It is easy to solve. There are eight 2 kOhm resistors on the board - 5 near MCU and 3 on another side. They set display segment current. (There are no other 2 kOhm resistors on the board). Replace them with smaller value. I found anything around 560 Ohm would be Ok. Smaller values can lead to overcurrent.

I also got a blue manual control box for this board. It is built around the same STC MCU. It's very useful for stepper testing but quite useless in production work - no need to buy. (I bought it for testing purposes only.) However it can easily be replaced with a simple 555 pulse generator on a breadboard so a bit overpriced.

[jaclerier]

Hi guys
I read and reread this post that intend to fix this board. I followed the steps since begin and the first thing that i've done was add another 74hc14 to buff the signal steps, this realy gave me a better board, but i still have the miss steps in all the velocities so i removed the opto acoupler and take the signal directily to 74hc14 added with this modification i have a terrible noise from de stepper motor, i could hear the miss steps. i've put again the optos but i removed all the optos of dir and i've done a jumper between the pin 2 with 4 and all the four axis works very well without miss steps. i removed also the others optor i left only the step and enable optor in.
Now i have one question, how i put the diodo to protect my boad of back emf from motor and the reley?
And sorry for my english

[Gall]

Now i have one question, how i put the diodo to protect my boad of back emf from motor and the reley?

For motors: Each winding needs four diodes, two at each output (8 diodes for one motor total). At each pin, one diode to ground (cathode to motor, anode to ground) and one to +12-36V (anode to motor, cathode to power bus). Diodes to ground are on the board already (at least my board has them). Just connect each of the motor outputs to the power rail with a diode (cathode to power rail), now it's Ok.

For the relay: just one diode between the relay winding pins, also connected backwards.

[jaclerier]

For motors: Each winding needs four diodes, two at each output (8 diodes for one motor total). At each pin, one diode to ground (cathode to motor, anode to ground) and one to +12-36V (anode to motor, cathode to power bus). Diodes to ground are on the board already (at least my board has them). Just connect each of the motor outputs to the power rail with a diode (cathode to power rail), now it's Ok.

For the relay: just one diode between the relay winding pins, also connected backwards.

Hi Gall tanks for your reply
take a look at the attachments marked in red an see if this right?

[jaclerier]

For motors: Each winding needs four diodes, two at each output (8 diodes for one motor total)

one more thing, i have this diode here. can i use it? will work?

[JohnStone]

As I want to prevent another blow of my drivers (thanks Mr. China - I'm not amused - definitely not!) I continue consdering more power issues. (listen Mr. China !)

Power off failure - more precisely:
When power off (especially with motors disconnected) the 5V will very probably cease long before the motor voltage in the big capacitors. Once again we see a violence of the clearly expressed requirements.
Unfortunately the motor voltage of each channel is separated by the reverse protection diode at the respective input. So if you connect motors to 3 channels they possibly survive the power off switching because the capacitors are discharged early enough. “Surprinsingly” the 4th cannel will die because it did not get rid of the motor voltage doue to the fact that there is no load at output. If you disconnect Z and switch on / off later this channel will die - “surprisingly”.

Another power consideration:
A member - Mariss Freimanis - in this forum shared some very interesting notions at differnt places. In summary he points out, that we need to consider the power coming from the motors (i.e. back EMV install condition) back to the drivers traveling through the internal or external protection diodes (the way taken does not matter) into the power capacitors. This can charge the capacitors to a dangerous overvoltage for the 6560 drivers. As there is a power separation for every driver (D15,25,35,45) the voltage can't go back to the PSU to be bufferd. It is very well understandable that the condition gets more dangerous if we applied a higher voltage initially.

Maximum ratings:
The same member stresses the fact that absolute maximum ratings are not automatically all true at same time. He ist right! So 3,5 Amps and simultaneously maximum voltage may be a serious problem. He votes for operation at reduced figures in order to have enough margin for safety reasons.

Some preliminary notions regarding a possible solution:
The intention of the separation of the voltage path (4 channels an 12V /5V) by diodes is primarly ment as a protection from reverse voltage.
Secondly they can prevent traveling noise from one channel to another. This can be true because every transient current at PWR+ will initate a corresponding current in the GND region between the drivers.
Summing up: Good idea - but - made worse by not considering other conditions above.

Now imagine the possible advantage of the following conditions:
1.
The back EMV from the motors does not occure simultaneously at each channel. If it can be shared (no diode separation) with the other capacitors it will be less serious.
Alternatively - if we want to keep the channel separation the capacitors need to be of much greater value if we exceed 24V at PSU side considerably in order to deal with the lesser safety margin.

2.
Adding voltage protection diodes of i.e. 36V would be another good idea. They possibly need to short circuit considerable energy! TBD

3.
Omitting the voltage separation by diodes would enable the big capacitors at motor voltage to supply the 12V/5V regulators. This can be a considerable help at power off condition. The 5V will be available down to 9V and possibly below. (5Volt + 2V voltage drop at each regulator) At 9V the motor voltage seems to be less dangerous.

4.
Do not operate your borad with open motor terminals. Connect a spare motor(s) or corresponding power resistors.

5.
Do not connect or switch the PSU output to the board under power. Please switch the mains and take the advantage of voltage rush in time.

6.
Ground connection from heat sink to pin 10 and 15 of each driver (PGNDA, PGNDB) or at least one of them.


Warning:
Please consider that this configuration will still not face the flaw at power on condition and might have other disadvantages. This is still an open and public thought experiment in order to evaluate some possible steps of modification.
So I ask you kindly not to modify your board just now as long you are not an expert and can conduct required measurement. (except item 4 to 6 - these are not dangerous.)

It would be easy to propose a complex setup nobody can build. But we need a real solution being as simple as possible. So give me some time for tinkering. But you are invited to share some proposals.
Regards
John

[Gall]

Hi Gall tanks for your reply
take a look at the attachments marked in red an see if this right?

Absolutely.

Please note, four diodes going to ground are probably already on the board (in the long row of diodes next to the row of connectors). You probably do not need to install them. But check the board, board versions may vary.

[Gall]

one more thing, i have this diode here. can i use it? will work?

Yes. Of course.

[JohnStone]

Hi,
got time to take some measurements. I tested with 24 V because this voltage seems to give the TB6560 a chance to survive.
If the PSU is switched on the voltage rises vey very fast while the VDD is stable after ca. 12 ms. The rise of VDD is a constant slope due to the fact that the voltage regulators are current limited to about 1 Amp. So they charge their capacitors with constant current.
The current into th 12 V regulator is about 26 mA (without the small blower). The two regulators take 5 mA each so the quiescent current of the TB6560 is about 4 mA.
The measurement above proves that at any start up the requirements of the data sheet are violated.
Now it would be quite easy to switch the motor voltage later on. But easy switching is destructive because the capacitor of the PSU is fully charged at this time and the capacitors of the motor voltage are in a discharged state. By switching on hundreds of amps will flow instantly and destroy any switch.

The only way to handle power requirements is an intelligent switching sequence along with voltage monitoring. I expected a simpler solution initially - sorry!
1. Start with discharging the capacitors at motor voltage (VM) via a resistor to GND. A Relay will do fine because ist will have ce NC contact active even in case of power loss.
2. Wait until the 5V ar stable
3. Charge the VM capacitors via a current limiting resistor. This can be the discharge relay using the NO contact.
4. Switch on full PSU voltage to VM. Second relay.
5. Monitor voltages and in case of failure disconnect PSU from VM and start the discharge sequence at item 1. The 5V need to remain stable until the VM capacitors are stable.

I found no simpler solution to do this sequence. I evaluate the PICAXE mircrocontroller. The M2 type will work between 1.8 to 5 Volt. This enebles a correct sequence down to 1.8V.
As driver I will use a ULN 2803 driver. Two relais and two resistors needed additionally. 1W resistors will be fine because thir load is of short duration.
The PICAXE micro can perform a nice and reliable reset for the TB6560 as well.

This are the results of my investigations. But I will not be able to build this soon because my wife is seriously ill and she needs my assistance for a time.

For all of you not being able to do such a solution i recommend as quick and dirty solution for power down sequence: Insert a diode 1n400x from every VM capacitor to the input pin of the 12 V regulator. Doing this you will supply the logic voltage VDD out of the VM capacitors until they are dischrged down to 9V (5V + 2*2V for regulators). So you have at least a power down sequence that seems to not destroy the TB6560. (but still not conforming the data sheet)

Regards
John

[Gall]

3. Charge the VM capacitors via a current limiting resistor. This can be the discharge relay using the NO contact.
4. Switch on full PSU voltage to VM. Second relay.

Hi,

Another approach to it is to use just one charge-discharge relay. To limit charge current, install a thermistor (one of NTC type). It has relatively high resistance when turned on. As current flows through it, the resistance drops dramatically.

PICAXE is a little bit overkill, an analog circuit would work just fine. A 555 is enough, or even a couple of transistors. The simpliest way to go is to connect 5V to the base of an NPN transistor via a 4.2V Zener diode and to connect charge-discharge relay to the collector. As 5V supply goes above approx. 4.8V, the transistor will go open and turn on the relay. A simple RC circuit may delay the turn-on. A similar approach can be taken to short the charge limiting resistor, either by monitoring current through it or just by time delay. It's a good idea to wire TB6560's ENABLE circuit to this circuit too, so that if something happens to the power, TB6560 will go disabled before 5V disappears.

I'm working on restoring optical isolation of this board. Looks like it is enough to cut traces in two places and remove 7805 and 7812 completely, replacing them with an isolated DC-DC converter for the input side and with a 5V supply for the output side.

Tonight I removed that wierd current control circuit completely, not by cutting traces. The board now has nice unpopulated SMD pads

[psny91]

I just got the 3-axis version of the tb6560 a few months ago, and just have gotten around to setting it up. Like many of you in this thread I have had my problems, but I haven't even been able to get the motors to turn. When I turn the system on, I can sure hear the motors as they make quite a bit of noise and vibrations, but they just do not turn. I am using Mach3 and really do not know what's wrong, if its a software or hardware problem. I have several suspicions though:

1.) I used the manuals that came with the controller and set up the ports and pins how it told it me to, yet I am not convinced that Mach3 is giving the controller information. The connection LEDS do come on and my computer recognizes the controller. I did have to get an LPT to USB converter cable, so I am not sure if that is affecting the signal.

2.) When I tested the voltage coming out of the x, y, z motor ports. I did get ~12V coming out of the x, but no voltage coming out of the y or z. Since I am putting 12 V into the system, shouldn't 12V be distributed to all of the axes?

Please Help! I really do not have much experience with these types of things. I do have access to both a multimeter and oscilloscope as I am at a University.

[doorknob]

1.) I used the manuals that came with the controller and set up the ports and pins how it told it me to, yet I am not convinced that Mach3 is giving the controller information. The connection LEDS do come on and my computer recognizes the controller. I did have to get an LPT to USB converter cable, so I am not sure if that is affecting the signal.

Are you saying that your computer does not have a built-in LPT port, so you are using a USB to LPT converter instead?

If so, Mach3 will probably not work with such a setup, rather it wants either an LPT port built in to the motherboard or an accessory LPT card (for example, plugged into a PCI slot).

[Gall]

Please Help! I really do not have much experience with these types of things. I do have access to both a multimeter and oscilloscope as I am at a University.

Another common problem is wrong configuration. These boards come in at least two versions having different pin assignment. Try both.

[JohnStone]

Hi Gall,
I agree with your thoughts excecpt that there is the condition that the power can fail for a certain short time and will come back. I could not imagine a simple solution facing this intermediate states.
While I have some picaxe available and darlington drivers this overkill (yes you are right) is the most simple way for me to build.
But I am eager to learn if someone found a smarter solution :-)

Question: What exactly did you de-populate on your board?

Regards
John

[psny91]

Are you saying that your computer does not have a built-in LPT port, so you are using a USB to LPT converter instead?

If so, Mach3 will probably not work with such a setup, rather it wants either an LPT port built in to the motherboard or an accessory LPT card (for example, plugged into a PCI slot).

Ahhh thanks so much! After using a mobo LPT port and fiddling with the dips and pins, I finally got them to turn, albeit pretty noisily, but they do turn.

[Gall]

Hi Gall,
I agree with your thoughts excecpt that there is the condition that the power can fail for a certain short time and will come back. I could not imagine a simple solution facing this intermediate states.

In older USSR made devices there was a quite common solution to that.

A time delay circuit was a Schmitt trigger (usually built from these big metal 1960's discrete transistors) with a capacitor at input. The capacitor was charged slowly from the power supply through a resistor. In case of power failure it was discharged very quickly through a diode. This circuit controlled a relay. Its most common usage was to connect a speaker to the output of an high power audio amplifier.

Another (very simple!) approach is to have a self-holding relay. Connect the winding of the relay to the power supply via the NO switch of this relay. To turn this circuit on, something like a momentary switch (may be a transistor) should be connected parallel to the NO group. Once turned on, this relay will hold its output until power off. Since this circuit is very robust, it is commonly used together with safety interlocks and/or ESTOP buttons. They should be of NC type and wired in series with the relay. This type of circuit is known as the "magnetic starter" in motor control center applications.

Of course, if you have a reason to install a MCU into your device, this MCU may control power on sequence as well.

Question: What exactly did you de-populate on your board?

Each channel has a current control circuit, the one in the center on this image:
http://www.cnczone.com/forums/attach...4&d=1283013610

Instead of just cutting a wire, I removed all three parts drawn from the dashed box - the 10k resistor, the pnp transistor and the capacitor. All these parts are easily accessible on the board and can be removed with any SMD-capable soldering iron with some solder wick. I did that because I have a SMD rework station and I do not like cutting traces.

Later I'll show photos how to make the board optically isolated. Now I'm doing that. It requires removal of 7812 and 7805 and replacing them with another power supply and cutting traces in about five places.

[914paul]

If this has already been suggested, I apologize -- this thread has gotten quite long and I haven't read it all. I have the cncgeeker drivers and, like many others, I've spent dozens of hours trying to get rid of the missed steps. I just stumbled onto using active low for the motor outputs and everything is so much smoother it's amazing. I have sherline half pulse off and step pulse at 15us and dir pulse at 5us. This is with unmodified boards. The rest of my config is: Zen 7x7, nema 17 (wimpy, I know), supply set to 20V, 1/8 stepping, 12in/min, Mach3. Has anyone else tried this?

[jaclerier]

Hi
I really don't know if it is better or not, but i down 36v to 24v to intent prevent issues and for my curiosity i measure the amper and i saw that amper keep at 3.20A even whe the four motor are on. three motor are 2A phase an one 3A phase, this board says that i need at least a PSU with 11A, but even when all is working i have just 3.2A. My question is, is that right or my PSU is wrong?

[Drools]

I'm sorry but I have read all the pages here but I was wondering if anyone has designed a daughter board with the best of the ideas posted here. Something done in Eagle maybe so that DIYers could easily route the board and populate.
Thanks.